Stop the sequins from falling off
First - never cut of that loose thread from which your sequins or pearls started falling off. This is the one you use to fix the situation! If long enough, just put the open end of your thread on a needle, gather your sequins (if lost, start by buying new ones - they can often be found in your local sewing or ribbon store, or if you're lucky you'll have a few to spare that came with when you bought your dress/top) and start adding them on. Depending on your sequin, be sure to make the right type of stitch. And if your broken thread is too short, still use it. In this situation, find a thread in the same color, and use it to "stitch down" the broken end. Once that is done and secured, use you new thread and start by fixing your sequin, one by one.